package text19090923;

import java.util.Scanner;

public class text19092301 {

	public static void main(String[] args) {
		Scanner in = new Scanner(System.in);
		int C; 
		int F = in.nextInt();
		C = (F - 32)*5/9;
		System.out.printf("%,4f",C);
		in.close();
	}	
}